Crop Weather Relationship of Chickpea under Late Sown Conditions in Northern Telangana Zone (NTZ)

In developing countries like India people obtain major portion of protein requirement of the body in the form of pulses. Chickpea is one of the major pulse crop which is very healthy as it supply roughly 60-65% carbohydrates, 18-22% protein, 6% fat and rich source of minerals and provides important vitamins such as riboflavin, niacin, thiamine, folic acid and carotene, a precursor of vitamin A (Eshan et al., 2023, Cokkizgin et al., 2025).
       
Chickpea is important rabi pulse crop cultivated in different parts of the country and world (Jain et al., 2023). Major states of India where chickpea is cultivated are Madhya Pradesh, Rajasthan, Karnataka, Uttar Pradesh, Andhra Pradesh, Gujarat, Jharkhand, Chhattisgarh and Telangana (Srinivas et al., 2025). India is the largest producer and consumer of pulses with a lion share of 42.6% of area and 28.3% of production globally (Agricoop, 2022). Chickpea contributes about 47% of the total pulse production and about 40% of total pulses growing area in the country. In India, chickpea is a premier pulse crop occupying 9.9 million hectares of land with a production of 11.9 million tonnes and with a productivity of 1192 kg ha^-1 (Indiastat, 2021). In Telangana, it is cultivated in 1.59 lakh hectares of area with a total production of 224 metric tonnes and with a productivity of 1407 kg ha^-1 with highest area and production in Kamareddy followed by Adilabad, Nirmal districts (Department of Agriculture Co-operation and Farmer Welfare, 2022).
       
As chickpea is a rabi, crop it requires cool weather for its growth but temperatures start rising from mid-February onwards which adversely affects crop growth and development resulting in early maturity of crop (Chand et al., 2010). From previous two decades, climate change has caused variations in the global temperature, leading to a negative impact on crops grown in arid and semi-arid countries. The best sowing time is crucial for the overall growth and development of the plants because chickpea crops are sensitive to temperature variations as early-sown crops are exposed to low temperatures (<5^oC) during their vegetative stage in December and January while late-sown crops are exposed to high temperatures (>35^oC) during their reproductive stage in February and March (Kumar et al., 2023).
       
As chickpea crop is a photo and thermosensitive crop, various sowing dates may affect the crop different vegetative and reproductive stages as a result of changes in temperature, sunshine hours and day length. Since chickpea needs cool, dry weather for better growth and development, it is grown in the winter months following by monsoon season. (Singh et al., 2022). Occurrence of high temperatures during flowering and pod formation under late-sown condition have a negative impact on the crop productivity. This is due to variations in temperature can affect the morphological, physiological and biochemical behaviour of the crop (Moradshahi et al., 2004, Patel et al., 1997). Present experiment was carried out to study the crop weather relationship of chickpea under different dates of sowing.

The investigation was carried out during Rabi season (2022) at the College Farm, Agricultural College, Jagtial, Professor Jayashankar Telangana State Agricultural University (18^o50’37" N and 78^o57’6" E and 243.4 m above MSL). The experiment was laid out in split plot design with six dates of sowing viz., 1^st November, 15^th November, 1^st December, 15^th December, 1^st January and 15^th January in main plots and three varieties viz., JG-14, NBeG-3 and NBeG-47 in sub-plots and replicated thrice. All recommended agronomic practices and plant protection measures were adopted to raise the crop. Daily weather data (maximum temperature, minimum temperature, morning relative humidity, evening relative humidity, bright sunshine hours, rainfall and day length) were collected from the meteorological observatory at the Regional Agricultural Research Station, Jagtial, throughout the crop-growing season. During various stages of chickpea growth, agrometeorological indices such as Growing Degree Days (GDD), Helio Thermal Units (HTU) and Photo Thermal Units (PTU) were calculated.
 
Growing degree days (GDD)
 
Growing degree days (GDD) concept was proposed to explain the relationship between growth duration and temperature. It is the mean temperature above base temperature. Mathematically, it can be expressed as

                                                                     
Where,
T_max = Maximum temperature (^oC).
T_min = Minimum temperature (^oC).
T_base = Base temperature (5^oC).
 
Helio thermal units (HTU)
 
The product of GDD and the actual number of hours of bright sunshine for a given day is represented by the Helio thermal units for that day. Using the following formula, the HTU for each phenophase’s duration was calculated.

 
Photo thermal units (PTU)
 
The product of GDD and day duration is represented by the photothermal units for a day. The formula below was used to calculate the total PTU for each phenol phase.
 

 
Correlation and regression analysis were carried out by using of IBM SPSS statistics software. Correlation between weather parameters and crop dry matter production, yield attributes and seed yield were carried out. Similarly, step wise regression analysis was used to derive a relation between weather parameters and dry matter production, yield attributes and seed yield.

Agrometeorological indices
 
Growing degree days (GDD)
 
During the crop growing season accumulated growing degree days (GDD) for different dates of sowing ranged from 1714 to 1753 with standard deviation of ±13.7 from sowing to physiological maturity. Delay in sowing resulted decrease of accumulated growing degree days due to decrease of number of days to attain physiological maturity. Similar results have also been reported by Eshan et al., (2023), Ragavendra et al., (2021) and Nikam et al., (2015). As reduction of number of days to physiological maturity decreases dry matter accumulation and ultimately yield.
 
Photothermal units (PTU)
 
Accumulated photothermal units for each growth stage under different sowing dates was calculated and presented in the Table 1. In case of crop sown on 15^th January showed maximum photo thermal units (20505) and minimum (19093) on 15^th November with a standard deviation of ±483.9.


 
Helio thermal units (HTU)
 
Cumulated Helio thermal units of each stage of crop are computed for different dates of sowing and shown in the Table 1. Results shows that HTU for crop from sowing to physiological maturity was in the range of 12466 to 13847 with a standard deviation of ±536.3.
 
Relationship between weather parameters and dry matter, yield and yield attributes
 
Maximum temperature
 
The correlation studies between dry matter production and maximum temperature (Table 2) showed negative correlation at P₂ (branching initiation to first flower), P₃ (first flower to first pod) and P₄ (first pod to maturity) was -0.87**, -0.60** and -0.84**, respectively and yield attributes, yield also showed negative correlation with maximum temperature.  Hence, the rise of temperature during different stages of the crop decreased photosynthesis rate as well as stomatal conductance resulted reduction of leaf area index, dry matter production, yield attributes and yield (Chakrabarti et al., 2013, Satpathi et al., 2022).


 
Minimum temperature
 
Correlation study between mean minimum temperature and dry matter production (Table 2) showed significant negative correlation at sowing to branching initiation (-0.63**), branching initiation to first flower (-0.66**) and first pod to maturity (-0.91**). The correlation study between minimum temperature and number of branches plant^-1, number of pods plant^-1, seed index and yield showed significantly negative correlation at first pod to maturity (P₄) stage ( -0.77**, -0.72**, -0.75** and -0.83**, respectively) and seed yield was negatively correlated at P₂ (-0.64**) also.
 
Mean temperature
 
Significant negative correlation was obtained between mean temperature and dry matter production at P₁ (-0.66**), P₂ (-0.89**) and P₄ (-0.928**) stages of crop. Number of branches plant^-1 were also significant negatively correlated with mean temperature at P₂ (-0.62**) and P₃ (-0.84**). Pods plant^-1 of chickpea was negatively correlated with mean temperature at P₁ (-0.64**) and P₄ (-0.81**). Seeds pod^-1 and seed index showed significantly negative correlation at P₂ (-0.86**) and P₄ (-0.67**), respectively. Seed yield of chickpea under different dates of sowing showed significant negative correlation with mean temperature at P₁ (-0.63**), P₂ (-0.82**) and P₄ (-0.85**).
 
T_max-T_min
 
Correlation between T_max-T_min and dry matter production of chickpea at harvest was showed significant negative correlation at P₂ (-0.66**) and P₃ (-0.65**). Number of branches plant^-1 (-0.66**) and seed index (-0.66**) was negatively correlated with T_max-T_min at P₃ stage. Seed yield was found significant negatively (-0.64**) correlated with T_max-T_min at P₂ stage of crop. However, T_max-T_min was significant positively (0.92**) correlated with seeds pod^-1 at P₂ stage.
 
Morning relative humidity (RH I)
 
Positive correlation (0.87**) was observed between dry matter production and morning relative humidity at branching to flowering stage (P₂). Number of pods plant^-1 showed significantly positive correlation with morning relative humidity at P₂ (0.62**) and P₄ (0.62**) stages. But number of seeds pod^-1 showed negative correlation (-0.74**) at P₂ stage. While, the seed index and seed yield of chickpea were significantly positive correlated (0.77** and 0.85**) with morning relative humidity at branching initiation to first flower stage (P₂).
 
Afternoon relative humidity (RHII)
 
Significantly positive correlation (0.84** and 0.73**) was observed between crop dry matter production and afternoon relative humidity at P₂ (branching initiation to first flower) and P₃ (first flower to first pod) stages. Correlation between branches plant^-1 and RH II showed significantly negative correlation (-0.63**) at sowing to branching initiation (P₁).        

Significantly positive correlation (0.59**) was observed for pods plant^-1 at branching initiation to first flower (P₂). Whereas, seeds pod^-1 showed significantly negative correlation (-0.71**) at branching initiation to first flower (P₂). At branching initiation to first flower (P₂) and first flower to first pod (P₃) afternoon relative humidity showed significantly positive correlation with seed index (0.73** and 0.80**) and seed yield (0.82** and 0.69**). The plant growth and development were improved with increasing humidity, as higher humidity conditions help to keep the stomata open to maintain the photosynthesis process and minimize evaporation process of the plants (Chia and Lim, 2022).

Wind velocity (WV)
 
Dry matter production of the chickpea was significant negatively correlated (-0.65%) with wind velocity at branching initiation to first flower (P₂). Number of branches plant^-1 and seeds pod^-1 were positively correlated (0.71** and 0.76**) with wind velocity at branching initiation to first flower (P₂) stage. Seed yield of chickpea crop sown at different dates was showed significantly negative correlation (-0.64**) with wind velocity at branching initiation to first flower (P₂) stage.
 
Bright sunshine hours (BSSH)
 
Dry matter production was significantly positive correlated (0.86**) with bright sunshine hours at branching initiation to first flower stage (P₂). Dry matter production, number of branches plant^-1 and number of pods plant^-1 showed significantly negative correlation (-0.76**, -0.77** and -0.71** respectively) with bright sunshine hour at first flower to first pod formation stage (P₃). Number of pods plant^-1 showed positive correlation (0.63**) at branching initiation to first flower (P₂). Number of seeds pod^-1 was significantly negative correlated (-0.72**) at branching initiation to first flower (P₂) formation stage. Similarly seed index was negatively correlated with BSSH at sowing to branching initiation (P₁) while seed index and yield of chickpea under different dates of sowing was positively correlated (0.75** and 0.83**) at branching initiation to first flower (P₂) formation stage.Higher radiation interception by the plant canopy with increase in bright sunshine hours intensifies photosynthesis. This leads to higher accumulation of dry matter by the crop thereby increasing its weight (Sah et al., 2019).
 
Evaporation (Eva)
 
Significantly positive correlation was existed between evaporation and DMP (0.89**), number of pods plant^-1 (0.62**), seed index (0.78**) and seed yield (0.85**) at branching initiation to first flower (P₂). However significant negative correlation was noticed between evaporation and dry matter production (-0.87**), number of branches plant^-1 (-0.78**), seeds pod^-1 (-0.74**), number of pods plant^-1 (-0.83**) and seed yield (-0.85**) at first pod formation to maturity stage (P₄).
 
Regression analysis
 
Stepwise regression analysis was performed to find out the critical weather parameters responsible for dry matter production, yield attributes and seed yield of chickpea. The regression models obtained were presented in the Table 3.


 
Regression models for prediction of dry matter production, yield attributes and yields of chickpea
 
Model I: Dry matter at physiological maturity
 
The minimum temperature at first pod formation to maturity (P₄), wind velocity at sowing to branching initiation (P₁) and maximum temperature prevailed from first flower to fist pod stage (P₃) accounted for 92% variation in dry matter production at physiological maturity.
 
Model II: Number of branches plant^-1
 
The maximum temperature at first pod formation to maturity (P₄) and first flower to first pod (P₃) phases has influenced the number of branches plant^-1 which accounted for 76% variation.
 
Model III: Number of pods plant^-1

Maximum temperature prevailed from first pod formation to maturity (P₄) accounted for 66% of total variation in production of number of pods plant^-1.
 
Model IV: Seed index
 
The maximum temperature at branching initiation to first flower (P₂) and bright sun shine hours at sowing to branching initiation (P₁) accounted for 78% variation in seed index of chickpea.
 
Model V: Seed yield
 
Minimum temperature at first pod formation to maturity stage (P₄) accounted for 68% variation in seed yield of chickpea.

Heat units required by the crop from sowing to maturity ranged from 1714 to 1753 GDD, PTU was ranged from 19093 to 20505 and HTU was ranged from 12466 to 13847. Minimum temperature from first pod formation to physiological maturity (P₄) stage accounted for 68% of total variation in seed yield of chickpea and minimum temperature at first pod formation to physiological maturity (P₄), wind velocity at sowing to branching initiation (P₁) and maximum temperature prevailed from first flower to fist pod formation stage (P₃) accounted for 92% variation in dry matter production at physiological maturity. From the crop weather relation, it is concluded that with delay of sowing crop exposed to abnormal weather conditions at different phenological stages resulted in reduction of crop growth and productivity.

The authors are grateful to Professor Jayashankar Telangana State Agricultural University for the providing financial assistance to carry out this experiment.

All authors declared that there is no conflict of interest.